So far I have found quite a bit of information on related family trees on myheritage.com (basically it got added automatically to my tree after filling in a couple) and on the following website: http://search.arch.be/
I got on my paternal tree up to:
Judocus Van Sever (1756 - 1830) x Barbara van Hemelrijk (1782 - 1843)
Franciscus Josephus Van Sever (? - 1783) x Barbara Soetewey (? - 1760) (They loved their Barbaras...)
Egidius Van Sever (? - 1744) x Gertrudis Van Baerode
Guilielmus Van Sever x Catharina Verplast
I can't get any further than Guililmus though, and the only references I found to him personally was on the other people's family trees. I'd like to be able to expand on my paternal line, but totally ran into a brick wall.
Facts that probably matter is that Van Sever is sometimes misspelled as Van Cever (and Van Severen), and they've always lived in Wezembeek (which is Wezembeek-Oppem nowadays)
Evidence of all paternal relationships are found on the abovementioned website, which is basically a collection of different official registrations. By going to "persons" and looking up "Van Sever" as a name, all of this can be found.
The only thing that I can not find evidence from is the last paternal link. I have seen Guilielmus' name appear as the godfather of one of the children of Egidius however, and since it's customary to make the grandfather godfather, that is a bit of supporting evidence. His actual fatherhood is based on secondary evidence from people's family trees on myheritage.com, however.